Tectonic vicariance versus Messinian dispersal in western Mediterranean ground beetles. Molopina

The complex geological history of the western Mediterranean region conceals the23 interpretation of the evolutionary history of its current fauna, as similar distribution patterns24 may have very different temporal and geographical origins. Particularly intriguing are somesubterranean species in islands, which origin is usually difficult to interpret as their strongly26 modified morphologies obscure their relationships. We studied subterranean taxa and their27 likely relatives of two groups of ground beetles in the western Mediterranean: the Duvalius28 lineage ("isotopic" Trechini) and Molopina (Pterostichini). We included specimens from the29 islands of Mallorca, Sardinia and Sicily, plus mainland Europe and north Africa. Phylogeneticrelationships were reconstructed with a combination of mitochondrial and nuclear data, and31 divergence dates were estimated with Bayesian methods using the same a priori molecular32 evolutionary rates for the same gene fragments in the two groups. In the Duvalius lineage, thesubgenus Trechopsis, including all the highly modified cave or nivicolous species, was found34 to be polyphyletic: the species from Mallorca was found to be of Pleistocene origin and sister35 to the less modified species of subgenus Duvalius from the same island, whereas the Algerian36 species of Trechopsis were, on the contrary, related to the Sicilian Duvalius, indicating a37 northern colonization route during the late Pliocene. Molopina was divided in three mainlineages: the genera Abax, Percus, and the Molops groups of genera. The basal diversification39 of the latter was dated within a temporal window (35-25 Ma) fully congruent with the tectonic40 opening of the western Mediterranean basin, and included six main lineages with uncertain41 relationships among them: the epigean genera (1) Molops and (2) Tanythrix; and the42 subterranean (3) Typhlochoromus (Eastern Alps), (4) Speomolops (Sardinia), (5) Henrotius43 (Mallorca) and (6) a strongly supported clade including the Pyrenean genera Zariquieya,44 Oscadytes and Molopidius. Despite the similar distribution of some of their subterranean taxa,45 the two studied groups show a strongly contrasting origin and mode of diversification. Whilethe Duvalius lineage had a recent origin, with complex colonization patterns and widespread47 morphological convergence among the subterranean species, the subterranean Molopina had48 an ancient vicariant origin resulting from the tectonic opening of the western Mediterranean49 basin.50